The authors tested whether 20 variants in the upstream promoter region, exon 1, and intron 1 of SAR1A were associated with HbF changes in response to HU compared to baseline in 32 adults with SCA from the Sickle Cell Pulmonary Hypertension Screening Study, prospectively followed up during two y of HU therapy. The gene discussed is SAR1A; the disease is pulmonary arterial hypertension.